Do some deep-sea, sediment-dwelling species of harpacticoid copepods have 1000-km-scale range sizes?

The range sizes of sediment-dwelling deep-sea species are largely unknown. Such knowledge is important because a deep sea composed in large part of species with 100-km-scale ranges would be very different from one composed predominantly of species with 1000-km-scale ranges. For example, the total species richness would be much greater in the first case than in the second. As a step towards the determination of the distribution of species' range sizes in the deep sea, we asked whether harpacticoid copepods (Crustacea) on the continental rise in the northeastern Pacific had 1000-km-scale range sizes. We chose harpacticoids because they occur widely in deep-sea sediments and thus are a typical deep-sea taxon. In addition, they have no pelagic stage in their life history, so they allow a conservative test of hypotheses about species' range sizes. We used morphology and gene-sequence data to assign individuals to species. At least 13.3% of the species we studied had 1000-km-scale ranges, raising the question of how these species maintain genetic continuity.

Detecting two-dimensional spatial structure in biological data.

Cliff and Ord (1973) made versatile methods available for the direct utilization of location data in the analysis of dispersion patterns, but their monograph has as yet seen little use in the ecological literature. Application of their weighted forms of Geary's c and Moran's I indices of spatial autocorrelation to some marine benthos data demonstrates a diversity of population structure not anticipated on the basis of more common measures of pattern. These indices provide objective means to evaluate numerous recent spatial models and hypotheses in geographical ecology and genetics. The procedures are particularly attractive because (1) they efficiently utilize data which are often wasted (i.e., sample coordinates), (2) their application puts few constraints on sampling designs which would otherwise be employed, and (3) they reveal and quantify pattern differences which are not obvious to the untrained eye.